Ion implantation is a critical process in semiconductor/microelectronic manufacturing. The ion implantation process is typically used in integrated circuit fabrication to introduce dopant impurities into semiconductor wafers. Generally speaking, with respect to semiconductor applications, ion implantation involves the introduction of ions from a dopant gas, also commonly referred to as dopant impurities, into a semiconductor wafer to alter the physical, chemical and/or electrical characteristics of the wafer in a desired manner. The desired dopant impurities are introduced into semiconductor wafers in trace amounts to form doped regions at a desired depth into the surface of the wafer. The dopant impurities are selected to bond with the semiconductor wafer to create electrical carriers and thereby alter the electrical conductivity of the semiconductor wafer. The concentration or dosage of dopant impurities introduced into the wafer determines the electrical conductivity of the doped region. In this manner, several impurity regions are created to form transistor structures, isolation structures and other electronic structures, which collectively function as a semiconductor device.
An ion source is used to generate an ion beam of ion species from a source dopant gas. The ion source is a critical component of the ion implantation system, which serves to ionize the dopant gas to produce certain dopant ions that are to be implanted during the implantation process. The ion source chamber comprises a cathode, such as a filament made of tungsten (W) or a tungsten alloy, which is heated to its thermionic generation temperature to generate electrons. The electrons accelerate towards the arc chamber wall and collide with the dopant source gas molecule in the arc chamber to generate a plasma. The plasma comprises dissociated ions, radicals, and neutral atoms and molecules of the dopant gas species. The ion species are extracted from the arc chamber and then separated from the other ionic species based on mass. Only ions in the beam based on a certain mass-to-charge ratio can pass through a filter. The selected mass of ions contains the desired ion species which is then directed towards the target substrate and implanted into the target substrate at the required depth and dosage.
Current semiconductor device technology utilizes a variety of dopant species in specific amounts to produce p-type and n-type semiconductors, both of which are considered building blocks for the manufacture of transistor and diode electronic devices. The difference in p-type and n-type dopants is primarily related to the charge carrying species introduced into the semiconductor crystal lattice. A p-type dopant is used to generate electron “holes” in the semiconductor material by creating electron deficiencies in the valence band while n-type dopants are used to generate free electrons in a semiconductor material. Antimony (Sb) is an example of a commonly used dopant species required for today's electronic devices. Sb is an n-type dopant with many desirable uses that continues to gain interest in the semiconductor industry. For example, Indium Antimonide is a narrow bandgap III-V semiconductor used as an infrared detector. Antimony is also used to form ultra-shallow p-n junctions in finFET devices; threshold voltage tuning of channels in MOSFETs; punch through stop halo implants in pMOS device; and source-drain regions in germanium n-MOSFETs.
Currently, solid sources of Sb are used as dopant materials. Elemental Sb metal can be used for ion implantation by placing it in close proximity to a filament. During ion implantation, the temperature of the filament is sufficiently high such that radiative heating causes Sb to evaporate and collide with electrons to create Sb-containing ions for doping. However, this method can cause Sb to deposit on the chamber walls or on the filament, shortening the filament lifetime. Solid compounds of Sb are also used as dopant sources, such as SbF3, SbCl3, and Sb2O3, but these compounds require heating to above 160° C. to generate a sufficient amount of vapor necessary for ion implantation. Additionally, all flow lines in the system are typically heated to prevent re-condensation of the solid sources of Sb before reaching the arc chamber.
Given the operational challenges of solid sources of Sb for implanting Sb-containing ions, gas sources of Sb have been contemplated. In particular, SbH3 and SbD3 have been proposed as gaseous sources of Sb, but these compounds are unstable and decompose at room temperature.
There is currently no viable Sb dopant source available today for ion implantation. There is an unmet need for a reliable Sb dopant source that can be used in traditional ion implantation systems.